I’m going to be doing a Webinar next week for the Silverlight Show highlighting the features of WCF RIA Services for validation. This is one of my favorite aspects of RIA Services because it makes validation so incredibly easy. You can use validation attributes from the System.ComponentModel.DataAnnotations namespace and they will be validated on both the client and server side. You can do programmatic validation on the server side and throw a ValidationException and it will get turned into client side validation errors for the appropriate entities. And you can do async validation calls to the server side and affiliate the errors with the entities yourself through a simple API. In all cases, the error get all hooked up in the entity base class so that it ties in perfectly with the built-in validation mechanisms of Silverlight.
So come check it out, next Wednesday at 1000 PST: